I just clicked on a thread (the "taking too long in the bathroom one") and it came up in a completely different format. The colour for the OP was different to the one I have in settings, there was a prominent banner on each of OP's posts saying "original poster" and, as I scrolled down I was seeing a "this is post 5 of 15" message.
I've just gone back to the thread and it now looks "normal".
FWIW I think that the "this is post 5 of 15" message is useful as it might deter more of the "cancel the cheque" type posts.
Did I hallucinate this MN?